Rasch model category probability curves for all items together in the AS-20 showing the likelihood that a participant with a particular coping ability will select a category.

<p><b>A.</b> The scale (<i>x</i>-axis) from +6 to -6 symbolizes the latent trait of health-related quality of life and the <i>y</i>-axis represents the probability of category being selected. Response categories: 0 “never”, 1 “rarely”, 2 “sometimes”, 3 “often” and 4 “always”. For any given point along this scale, the category most likely to be chosen by a participant is shown by the category curve with the highest probability. At no point, was category 1 the most likely to be chosen and appears to be interchangeable with categories 0 and 2, resulting in disordered thresholds. <b>B</b>. Ordered thresholds following category re-organization and reducing the number of categories from 5 to 3 for the category probability curves seen in Fig A. Thresholds represent boundaries along the scale where the probability of a response category being chosen changes from one to the next.</p>